Thermal behaviour of network components depending on outdoor weather conditions

The liberalization of the power market and the increasing number of regenerative energy producers (esp. windparks) cause an increasing current load on existing transmission systems. As a result, power utilities and system operators are currently looking for opportunities to increase the capacity of the existing overhead lines (OHL) without increasing the risk of equipment or system failure due to higher loading and an accelerated aging of the transmission infrastructure. Several monitoring systems to increase the capacity of the existing transmission lines are in service. But all components of the electrical circuit have to be able to carry the increased current load. It is also necessary to take care on ageing behaviour of existing joints and terminations in transmission and distribution systems. Most previous investigations concentrate on the ampacity of overhead lines depending on varying weather conditions like ambient temperature, wind speed and direction and solar radiation. This paper will present a contribution to the thermal behaviour of other components in transmission systems, especially circuit breakers, disconnectors, current transformers and line connectors depending on weather conditions. Therefore thermal network calculations are compared and equalized to experiments with real equipment. Increase or decrease of maximum allowable current load of the several components is discussed. The investigations show, that the ampacity of the components depending on the ambient conditions are varying. So the ambient temperature can easily be used, because all components react alike and the ambient temperature does not change so frequently in time and region. The wind speed in contrast changes very fast, is regional very volatile and the components react very divers.